Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• absorption of quinoxaline-fused [6]helicene 10a was red-shifted by 19 nm (Table 7). Compounds 10 exhibited almost a solvent independence of UV–vis absorption spectra (Supporting Information File 1, Figure S41). The optical band gaps (Egopt), estimated from the onset point of the absorption spectra, for [6

• distortion angle of 50.5° is the smallest in the series. The photophysical properties of the synthesized [6]helicenes were compared to the parent carbazole-based [6]helicene. A spectrophotometric analysis of the quinoxaline-fused helicene displayed a moderate absorption red-shift (19 nm) and reduced optical

Chemical constituents of Chaenomeles sinensis twigs and their biological activity

• Joon Min Cha,
• Dong Hyun Kim,
• Lalita Subedi,
• Zahra Khan,
• Sang Un Choi,
• Sun Yeou Kim and
• Chung Sub Kim

Beilstein J. Org. Chem. 2020, 16, 3078–3085, doi:10.3762/bjoc.16.257

• which the results were expressed as a percentage of the control group (untreated cells). Chemical structures of compounds 1–13. Structure elucidation of compound 1. (A) Key COSY (blue bold) and HMBC (red arrows) correlations of 1. (B) Key NOESY (black dashed) correlations of 1. The 3D structure of 1 was

Semiautomated glycoproteomics data analysis workflow for maximized glycopeptide identification and reliable quantification

• Steffen Lippold,
• Arnoud H. de Ru,
• Jan Nouta,
• Peter A. van Veelen,
• Magnus Palmblad,
• Manfred Wuhrer and
• Noortje de Haan

Beilstein J. Org. Chem. 2020, 16, 3038–3051, doi:10.3762/bjoc.16.253

• glycopeptide clusters detected by GlycopeptideGraphMS. Representative GlycopeptideGraphMS output for peptides of interest. Assigned compositions were identified using MS/MS data via Byonic (green) or manual assignment (blue) or by MS1 only (red, GlycopeptideGraphMS with additional accurate-mass and isotopic

• pattern check of the raw data). The assignment of the compositions is based on information from all replicates. Lines between compositions indicate the mass difference for Hex (yellow), HexNAc (blue), HexHexNAc (green), Fuc (red), and NeuAc (purple). * Indicates potential deconvolution errors and

Metal-free nucleophilic trifluoromethylselenolation via an iodide-mediated umpolung reactivity of trifluoromethylselenotoluenesulfonate

• Kevin Grollier,
• Alexis Taponard,
• Arnaud De Zordo-Banliat,
• Emmanuel Magnier and
• Thierry Billard

Beilstein J. Org. Chem. 2020, 16, 3032–3037, doi:10.3762/bjoc.16.252

• form the CF3Se–C(sp3) bond. This chemistry is the prerogative of the CF3Se− anion (Scheme 1) [37][38][39][40]. However, the formation of this selenium species requires the tedious use of red elemental selenium [41] and also suffers from stability issues. To circumvent these drawbacks, a copper complex

• substitution. This is adequate with the observed results. Noteworthy, the supposed formation of I2 was strengthened by the appearance of a red-brown color of the reaction media which faded after the addition of sodium thiosulfate. As demonstrated in the sulfur series [49], the in situ formation of an alkyl

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• are highlighted in lilac; cyclopentane structures forged by the all-carbon [3 + 2] cyclization are labeled in red). (A) The intermolecular all-carbon [3 + 2] cyclization features as the key reaction. (B) The intramolecular all-carbon [3 + 2] cycloaddition features as the key reaction. Representative

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• that the fluorescence is significantly red shifted (about 30 nm) with respect to that of the corresponding diethyl aryl phosphates (see Figure 1 and Figure 2). On the other hand, when focusing on compound 3a, we noticed the presence of two emission bands located at 307 and 360 nm, respectively (see

• yields but under very mild conditions with no need of any (photo)catalyst or additive, despite the scope of the process is in part limited since the presence of at least one electron-withdrawing group on an aromatic ring completely suppressed the reaction. Emission spectrum of compound 1e (red) and of

• diethyl p-tert-butylphenyl phosphate (black) in methanol. Emission spectrum of compound 1h (red) and of diethyl p-cyanophenyl phosphate (black) in methanol. Emission spectrum of compound 3a in methanol (black) and in a methanol/TFE 4:1 mixture (red). Emission spectrum of 3c in MeOH (dotted line) and in

Secondary metabolites of Bacillus subtilis impact the assembly of soil-derived semisynthetic bacterial communities

• Heiko T. Kiesewalter,
• Carlos N. Lozano-Andrade,
• Mikael L. Strube and
• Ákos T. Kovács

Beilstein J. Org. Chem. 2020, 16, 2983–2998, doi:10.3762/bjoc.16.248

• correlation. Abundance ratios for each genus and replicate (points) in the control community compared to the WT-treated (A) and to the sfp-treated community (B). Red-box plots highlight the statistical significance, which is defined as P ≤ 0.05 (*), P ≤ 0.01 (**), and P ≤ 0.001 (***). The relative abundance

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• ). Fluorescence resonance energy transfer (FRET) relies on the distance-dependent transfer of energy from a donor fluorophore to an acceptor fluorophore. Genetically encoded fluorophores, such as green fluorescent protein (GFP) and related blue, cyan, yellow and red fluorescent proteins have provided the ability

• 310 nm excitation. However, it folds upon binding to dsDNA, thereby changing the efficiency of the FRET process between the two fluorophores and exhibiting a significant red shift in the emission spectrum (Figure 4B). Compound 3 emits at 535 nm upon 310 nm excitation in the presence of dsDNA. These

• polymerization reaction between polydiacetylene. PDA liposomes turn colorless to red upon formation of cross-linked liposomes. The fluorescence of the naphthimide is completely quenched due to the energy transfer from the fluorophore to the cross-linked polymer. However, addition of LPS restores the fluorescence

Naphthalonitriles featuring efficient emission in solution and in the solid state

• Sidharth Thulaseedharan Nair Sailaja,
• Iván Maisuls,
• Jutta Kösters,
• Alexander Hepp,
• Andreas Faust,
• Jens Voskuhl and
• Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

• ) substituted γ-diphenylnaphthalonitriles, which can be attributed to a weak π-donor capability of these groups. On the other hand, the methoxy- (OMe), methylsulfanyl- (SMe) and dimethylamino- (NMe2) substituted compounds exhibit a progressive red-shift in emission compared to H, Me and t-Bu due to a growing π

• -electron donating capability. Interestingly, upon aggregation in water-containing media, H, Me and t-Bu show a slight red-shift of the emission and a blue-shift is observed for OMe, SMe and NMe2. The crystal structure of Me allowed a detailed discussion of the structure–property relationship. Clearly, N

• , the π-donor nature of the substituents on the phenyl ring constitutes the main parameter that influences the photophysical properties, such as excited state lifetimes and photoluminescence quantum yields. Hence, a series of highly luminescent materials from deep blue to red emission depending on

Construction of pillar[4]arene[1]quinone–1,10-dibromodecane pseudorotaxanes in solution and in the solid state

• Xinru Sheng,
• Errui Li and
• Feihe Huang

Beilstein J. Org. Chem. 2020, 16, 2954–2959, doi:10.3762/bjoc.16.245

• . Color code: C, gray; Br, orange; O, red; and H, white. CH∙∙∙π distances (Å): 2.778, 2.886, 2.778, and 2.886; CH···Br distances (Å): 2.925 and 2.925. 1H NMR spectra (500 MHz, CDCl3, 298 K): (a) 6.00 mM G; (b) 3.00 mM G + 3.00 mM H; and (c) 6.00 mM H. NOESY spectrum of a solution of H and G (500 MHz

• , chloroform-d, 298 K). Normalized UV–vis spectra: H (black); H upon adding 0.5 equiv of G (red); and H upon adding 1 equiv of G (blue). [H] = 3.00 mM. Chemical structures and schematic representation of (a) the pillar[4]arene[1]quinone H; (b) 1,10-dibromodecane (G); and (c) schematic representation of the

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• couple noted E°ox/red [27]. After the addition of SF6, a stationary current is clearly observed before the acetonitrile reduction [28]. The electrochemial response of SF6 is related to a reproducible stationnary cathodic current. The intensity of the limiting current (plateau intensity) directly depends

UV resonance Raman spectroscopy of the supramolecular ligand guanidiniocarbonyl indole (GCI) with 244 nm laser excitation

• Tim Holtum,
• Vikas Kumar,
• Daniel Sebena,
• Jens Voskuhl and
• Sebastian Schlücker

Beilstein J. Org. Chem. 2020, 16, 2911–2919, doi:10.3762/bjoc.16.240

• and 215 nm. Both absorption bands can be attributed to π→π* transitions within the GCP chromophore. On the other hand, GCI ethyl amide exhibits a slightly red-shifted absorption band covering the entire region below 370 nm with two peaks at 320 and 244 nm which are also assigned to π→π* transitions of

• the GCI chromophore. The red-shift in the spectral positions of the GCI peaks with respect to those of the GCP peaks is due to the extended conjugation induced by the indole ring of GCI. We chose 266 nm and 244 nm as laser excitation wavelengths for UVRR spectroscopy. The 266 nm excitation was chosen

Incorporation of a metal-mediated base pair into an ATP aptamer – using silver(I) ions to modulate aptamer function

• Marius H. Heddinga and
• Jens Müller

Beilstein J. Org. Chem. 2020, 16, 2870–2879, doi:10.3762/bjoc.16.236

• a) 1af, b) 1bf, c) 1cf, and d) 1df in the absence (red line) and presence of increasing amounts of Ag(I). The melting temperatures in the presence of 0.0 and 1.0 equiv of Ag(I) are given, too. Conditions: 1 μM oligonucleotide, 50 mM NaClO4, 5 mM MOPS buffer (pH 6.8). The two systems devised to

• ): 1af (red), 1bf (yellow), 1cf (green), and 1df (blue) (n = 3). Conditions: 1 μM oligonucleotide, 300 mM NaClO4, 5 mM Mg(ClO4)2, and 20 mM MOPS buffer (pH 7.4). Elution of the aptamers from the ATP-agarose gel in the presence of 1 equiv of Ag(I): 1af (red), 1bf (yellow), 1cf (green), and 1df (blue) (n

Changed reactivity of secondary hydroxy groups in C8-modified adenosine – lessons learned from silylation

• Jennifer Frommer and
• Sabine Müller

Beilstein J. Org. Chem. 2020, 16, 2854–2861, doi:10.3762/bjoc.16.234

• various Pd-catalyzed reactions. Comparing the two reaction paths, the overall yield of the desired adenosine derivative 8 was increased from 2% to 12% over 7 reaction steps by changing the protecting group strategy. Characterization and assignment of the TBDMS isomers via HSQC (red) and HMBC (blue) NMR

On the mass spectrometric fragmentations of the bacterial sesterterpenes sestermobaraenes A–C

• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2020, 16, 2807–2819, doi:10.3762/bjoc.16.231

• fragment ion m/z (PMAm/z), in which fully contributing carbons are marked by red dots, partially contributing carbons by green dots, and carbons that do not contribute remain without a mark (Figures 2–4, vide infra). Because usually multiple fragmentation reactions lead to the formation of the ions

• ) and sestermobaraol (7) from Streptomyces mobaraensis. Position-specific mass shift analyses for 1. Carbons that contribute fully to the formation of a fragment ion are indicated by red dots, partially contributing carbons are marked by green dots, and unlabelled carbons do not contribute and are thus

• cleaved off by the fragmentation reaction. Position-specific mass shift analyses for 2. The carbons that contribute fully to the formation of a fragment ion are indicated by red dots, partially contributing carbons are marked by green dots, and unlabelled carbons do not contribute and are thus cleaved off

Synthesis and investigation of quadruplex-DNA-binding, 9-O-substituted berberine derivatives

• Jonas Becher,
• Daria V. Berdnikova,
• Heiko Ihmels and
• Christopher Stremmel

Beilstein J. Org. Chem. 2020, 16, 2795–2806, doi:10.3762/bjoc.16.230

• 3a–e decreased upon the addition of 22AG or a2 and new, slightly red-shifted absorption bands developed (Figure 1A; cf. Supporting Information File 1, Figure S1). During most of the titrations, the formation of an isosbestic point was observed. However, in several cases it clearly faded away at the

• unit and was the strongest with a chain length of n = 5 (Figure 3). In the case of a2, the positive band of this G4-DNA at 265 nm showed only small fluctuations upon the interaction with the ligands, whereas the intensity of the broad red-shifted shoulder at 295 nm slightly increased at higher LDR. In

• titrations with 22AG and a2 clearly revealed the association of the derivatives 4a–e with G4-DNA (Figure 1). Specifically, the red shift and hypochromism of the absorption band along with the pronounced increase of the emission intensity are typical for quadruplex-bound ligands [17][18][19][20][21][22

3-Acetoxy-fatty acid isoprenyl esters from androconia of the ithomiine butterfly Ithomia salapia

• Florian Mann,
• Daiane Szczerbowski,
• Lisa de Silva,
• Melanie McClure,
• Marianne Elias and
• Stefan Schulz

Beilstein J. Org. Chem. 2020, 16, 2776–2787, doi:10.3762/bjoc.16.228

• 68 (A), m/z 69 (B), and m/z 280 (C). Mass spectra and fragmentation of A: isoprenyl (3-methyl-3-butenyl) 9-octadenoate (9) and B: prenyl (3-methyl-2-butenyl) 9-octadecenoate (10). Red arrows show characteristics in the mass spectra differentiating prenyl and isoprenyl esters. Mass spectra and

• leading to the observed regioisomers of the isoprenyl esters. All acids shown were found in form of their isoprenyl esters. (Z)-9-Hexadecenoic acid is obtained from palmitic acid by a Δ9-desaturase (ds). Malonate elongation and reduction (red) leads to (Z)-3-hydroxy-11-octadecenoic acid, an intermediate

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through “turn-on” fluorescence response

• Rakesh Biswas,
• Surya Ghosh,
• Shubhra Kanti Bhaumik and
• Supratim Banerjee

Beilstein J. Org. Chem. 2020, 16, 2728–2738, doi:10.3762/bjoc.16.223

• , Figure S10b and 10c). The absorption maxima red shifted slightly and increased scattering was observed at higher amounts of ATP. The A0–0/A0–1 values were also found to decrease upon formation of the co-aggregates with ATP (Supporting Information File 1, Table S5). The small-chain analogue, PBIm4 (100 µM

Enzyme-instructed morphological transition of the supramolecular assemblies of branched peptides

• Dongsik Yang,
• Hongjian He and
• Bing Xu

Beilstein J. Org. Chem. 2020, 16, 2709–2718, doi:10.3762/bjoc.16.221

• nanofibers in the HeLa cells. Then, we used confocal laser scanning microscopy (CLSM) to examine whether these compounds deliver RPE into HeLa cells. After mixing R-phycoerythrin (RPE) [49], a red fluorescent protein, with 1 or 2 at different concentrations, we incubated the mixtures with HeLa cells for 2 h

• and 4 h. While the control cells (without adding 1 or 2) showed little fluorescence, the cells treated with RPE and 1 or 2 started to show many red fluorescent puncta inside the cells after 2 h. The puncta remained inside the cells at 4 h and showed little change (Figure 6). These results indicate

• HeLa cells treated with a mixture of RPE (8 μg/mL) and A) 1 (400 μM) or B) 2 (400 μM) after 2 h and 4 h of incubation. Blue: nucleus, red: RPE. Synthetic route to the branched peptides. (i) HBTU, DIPEA, DMF, 12 h, rt, (ii) TFA, 2 h, rt, and (iii) 20% piperidine in DMF, 2 h, rt. Supporting Information

A heterobimetallic tetrahedron from a linear platinum(II)-bis(acetylide) metalloligand

• Matthias Hardy,
• Marianne Engeser and
• Arne Lützen

Beilstein J. Org. Chem. 2020, 16, 2701–2708, doi:10.3762/bjoc.16.220

• : red – iron, white – platinum, orange – phosphorous, blue – nitrogen, grey – carbon. Hydrogen atoms are omitted for clarity. The stereogenic centers are defined in the schematic tetrahedra. Stepwise assembly of the heterobimetallic tetrahedron 4, starting from 4-ethynylaniline (1) and trans-[Pt(PBu3

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)–dipicolylamine complexes

• Lena Reinke,
• Julia Bartl,
• Marcus Koch and
• Stefan Kubik

Beilstein J. Org. Chem. 2020, 16, 2687–2700, doi:10.3762/bjoc.16.219

• water/methanol 1:2 (v/v). These anions caused the bright red solutions of the nanoparticles to change their color because of nanoparticle aggregation followed by precipitation, whereas halides or oxoanions such as sulfate, nitrate, or carbonate produced no effect. The sensitivity of phosphate sensing

• formed, the solutions either lose their color because of nanoparticle precipitation or they adopt a different color. Dispersed spherical AuNPs with a diameter of ca. 10 nm lead to intensely colored red solutions, for example, which turn purple or blue upon nanoparticle aggregation because the localized

• anions induced visual changes in the solutions of the functionalized AuNPs. To this end, a nanoparticle solution, which was colored bright red in the absence of anions, was distributed over eleven glass vials. Then, aqueous solutions of the sodium salts of various anions (NO3−, Cl−, Br−, I−, SO42−, HCO3

A consensus-based and readable extension of Linear Code for Reaction Rules (LiCoRR)

• Benjamin P. Kellman,
• Yujie Zhang,
• Emma Logomasini,
• Eric Meinhardt,
• Karla P. Godinez-Macias,
• Austin W. T. Chiang,
• James T. Sorrentino,
• Chenguang Liang,
• Bokan Bao,
• Yusen Zhou,
• Sachiko Akase,
• Isami Sogabe,
• Thukaa Kouka,
• Elizabeth A. Winzeler,
• Iain B. H. Wilson,
• Matthew P. Campbell,
• Sriram Neelamegham,
• Frederick J. Krambeck,
• Kiyoko F. Aoki-Kinoshita and
• Nathan E. Lewis

Beilstein J. Org. Chem. 2020, 16, 2645–2662, doi:10.3762/bjoc.16.215

• symbols were proposed by Krambeck et al. [10]. The initial names are ligand (“ ... ”), continuation (“ _ ”), and possible branch (“ | ”). Each uncertainty operator in the last four example columns can be replaced by the substring in red to achieve the behavior described in the column header. For a more

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• replacement of sulfur by nitrogen atoms in the tetra- and hexacyclic systems leads to a red-shift in absorption, a decrease in oxidation potential and energy gap. On the other hand, the replacement of a thiophene ring by benzene leads to the opposite effects. Keywords: Buchwald–Hartwig amination; Cadogan

• heteroacenes exhibited one vibronically well-resolved strong absorption band in the UV-regime of 250–360 nm which we address to the π–π* transition corresponding to the HOMO–LUMO energy gap. The absorption maximum is gradually red-shifted from 318 nm for TTA and with increasing number of pyrrole rings to 330

• only slightly red-shifted. The effect of benzannulation in 19 compared to H-SN4 13 as well results only in small differences, which, however, become larger in comparison to hexacyclic heteroacene 22 showing the largest bathochromic shift in the series (Figure S6, Supporting Information File 1). The

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• spectra. These bands are indicative of the radical anion NDI•− (Figure 4a–c, red curves) [59]. The radical character of NDIC8 was additionally confirmed by spectroelectrochemical EPR measurements, which showed an isotropic signal with a g-value of 2.004 (Figure S17 in Supporting Information File 1). Upon

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• were dried on a slide glass. C60 was tested in powder form on a slide glass. Molecular model of the complex TBTQ-(OG)6 C60 in water, as generated by DFT calculations. (a) Side-view; (b) top-view; (c) hydrophobic surface diagram. In part, H atoms were omitted for clarity (yellow: C, red: O, blue: N